Advertisements
Advertisements
Question
The electric field at a point associated with a light wave is `E = (100 "Vm"^-1) sin [(3.0 xx 10^15 "s"^-1)t] sin [(6.0 xx 10^15 "s"^-1)t]`.If this light falls on a metal surface with a work function of 2.0 eV, what will be the maximum kinetic energy of the photoelectrons?
(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)
Advertisements
Solution
Given :-
`E = 100 sin [(3 xx 10^-15 "s"^-1)t] sin [(6 xx 10^-15 "s"^-1)t]`
= `100 xx 1/2 cos [(9 xx 10^15 "s"^-1)t] - cos[(3 xx 10^15 "s"^-1)t]`
The values of angular frequency `ω` are `9 xx 10^15` and `3 xx 10^15`.
Work function of the metal surface, `phi = 2 "eV"`
Maximum frequency,
`v = ω_(max)/(2pi) = (9 xx 10^15)/(2pi) Hz`
From Einstein's photoelectric equation, kinetic energy,
K = hv - `phi`
`⇒ K = 6.63 xx 10^-34 xx (9 xx 10^15)/(2pi) xx 1/(1.6 xx 10^-19) - 2 "eV"`
⇒ K = 3.938 eV
APPEARS IN
RELATED QUESTIONS
The work function for a certain metal is 4.2 eV. Will this metal give photoelectric emission for incident radiation of wavelength 330 nm?
Write Einstein’s photoelectric equation?
point out any two characteristic properties of photons on which Einstein’s photoelectric equation is based ?
Define the terms (i) ‘cut-off voltage’ and (ii) ‘threshold frequency’ in relation to the phenomenon of photoelectric effect.
Using Einstein’s photoelectric equation shows how the cut-off voltage and threshold frequency for a given photosensitive material can be determined with the help of a suitable plot/graph.
The frequency and intensity of a light source are doubled. Consider the following statements.
(A) The saturation photocurrent remains almost the same.
(B) The maximum kinetic energy of the photoelectrons is doubled.
A small metal plate (work function φ) is kept at a distance d from a singly-ionised, fixed ion. A monochromatic light beam is incident on the metal plate and photoelectrons are emitted. Find the maximum wavelength of the light beam, so that some of the photoelectrons may go round the ion along a circle.
Consider the situation of the previous problem. Consider the faster electron emitted parallel to the large metal plate. Find the displacement of this electron parallel to its initial velocity before it strikes the large metal plate.
(Use h = 6.63 × 10-34J-s = 4.14 × 10-15 eV-s, c = 3 × 108 m/s and me = 9.1 × 10-31kg)
Use Einstein's photoelectric equation to show how from this graph,
(i) Threshold frequency, and
(ii) Planck's constant can be determined.
Choose the correct answer from given options
Photons of frequency v are incident on the surface of two metals A and B of threshold frequency 3/4 v and 2/3 v, respectively. The ratio of maximum kinetic energy of electrons emitted from A to that from B is
The wavelength of a photon needed to remove a proton from a nucleus which is bound to the nucleus with 1 MeV energy is nearly ______.
A student performs an experiment on photoelectric effect, using two materials A and B. A plot of Vstop vs ν is given in Figure.
- Which material A or B has a higher work function?
- Given the electric charge of an electron = 1.6 × 10–19 C, find the value of h obtained from the experiment for both A and B.
Comment on whether it is consistent with Einstein’s theory:
Einstein proposed that light energy is absorbed in discrete packets called what?
In \[E=h\nu\], what does \[\nu\] represent?
What happens to photon energy when frequency increases?
Which expression gives the maximum kinetic energy of emitted photoelectrons?
How is the work function related to the threshold frequency \[\nu_0\]?
Which expression gives the threshold frequency?
How can maximum kinetic energy be written in terms of stopping potential \[V_0\]?
Why does the maximum kinetic energy of photoelectrons increase when frequency increases?
